This invention relates to manufacture of papermaking fabrics and particularly to wet felts and occasionally dryer fabrics.
Over the years, papermakers have used the developments in wet felt design to improve water removal in the presses of papermaking machinery. With the advent of monofilament and multifilament yarns in the 1960's, "batt-on-bare" and "batt-on-mesh" designs were introduced. In these designs, carded batts are needled into woven base fabrics.
Conventionally, several layers of batt are cross-lapped onto the base fabric in the cross-machine direction. For example, see U.S. Pat. No. 3,257,259. When the batts are cross-lapped upon the base fabric for needling, the fibers are generally oriented in the cross machine direction rather than the machine direction. The starting line and ending line of the batt laying process forms a butt joint across the width of the fabric. This joint causes vibrations when passing through the press rolls. This problem is more acute when a pre-needled batt is used. In the case of wet felts, water must be pressed from the felt for water removal from the paper fiber matt. Cross-machine oriented fibers are thought to restrict the lateral movement of the water and adversely affect water removal from the sheet.
In view of these disadvantages of applying the web cross-machinewise, some felt makers have started to investigate the possibility of using batts having machine direction oriented fibers on the felts. The benefits of such batts can be twofold: (1) By eliminating the butt joint in the batt, the tendency of nip roll bounce is greatly reduced; and (2). The surface of such felts is exceptionally smooth and lacks needle marks. This not only enhances the water removal due to more uniform pressure application from the press rolls to the sheet, but also improves the surface quality of the sheet for the lack of needle marks. However, the technology and machinery to orient the batt and fibers on the base in the machine direction has been lagging.
Related U.S. Pat. Nos. 3,879,820 and 3,920,511 disclose a papermaker's felt and method in which the fibers are oriented substantially longitudinally to make a substrate by using numerous transfers of the batt upon aprons, reorientations along tortuous paths, and other batt manipulations in a rather complicated manner. A batt is then needled to the substrate crosswise to the felt travel.
U.S. Pat. Nos. 4,553,289, 1,953,457, and 3,713,933 relate generally to the art of building up fibrous batts either in juxtaposed or superposed relation. In the first two patents, general batts are reoriented 90 degrees by using angularly disposed guide rods so that the resulting batt is aligned lengthwise with a conveyer. These patents are related only generally and not directly to the present invention.
Accordingly, an object of the present invention is to provide an improved method and apparatus for making paper-making fabrics having a machine direction fiber batt in which applicating of the batt onto the base fabric and needling are carried out in a simplistic and efficient manner.
Another object of the invention is to provide a method and apparatus for making a papermakers felt which includes a fiber batt needled into a base fabric and the fibers in the fiber batt extend generally in the machine direction to facilitate water removal as well as to improve the sheet quality.
Another object of the invention is to provide a method and apparatus for making a papermakers felt wherein vibrations caused by the running of a felt on the papermaking machine are reduced.
Still another object of the invention is to provide a wet felt having machine direction oriented fibers which are laid upon a base fabric and needled without excessive fiber manipulation.